光纤布拉格光栅滤波型甲烷浓度测量系统设计

Design of fiber Bragg grating filtered methane concentration measurement system

针对甲烷浓度测量过程中,系统测量易受外界环境、气室不稳定等因素的影响,存在测量结果不准确的问题,设计了一套适用于低浓度甲烷气体测量的检测系统。首先,根据甲烷的吸收光谱结合现有光源的带宽选择甲烷2ν3带的R(4)支(1 650.955 nm)作为吸收峰;其次,根据光纤光栅的温度敏感特性,测量系统中加入参考光栅,解决了温度变化影响气体浓度精确测量的问题;然后,运用ZEMAX软件对设计的气室进行仿真模拟和优化,气室对甲烷近红外激光的耦合效率达到93.2%。通过实验验证了该气室的高耦合效率和高稳定性;最后,搭建测量实验系统,进行了系统的标定、系统技术指标的计算和气体浓度测量。测量结果表明,测量系统的灵敏度为0.02 mV/ppm,测量系统的稳定度为0.12%,最大测量相对误差为0.149%,系统测量的示值与理论值具有良好的线性关系,具有稳定可靠、精度高、抗干扰能力强等优点。

Aiming at the problem that the system measurement is susceptible to the external environment,unstable gas chambers and other factors,and inaccurate measurement results exist during the measurement process of methane concentration,a detection system suitable for low concentration methane gas measurement is designed.Firstly,according to the absorption spectrum of methane combined with the bandwidth of the existing light source,the R(4)branch(1650.955 nm)of the methane 2ν3 band is selected as the absorption peak.Secondly,according to the temperature sensitive characteristic of the fiber grating,a reference grating is added to the measurement system to solve the problem that the temperature change affects the accurate measurement of gas concentration.Then,the ZEMAX software is used to simulate and optimize the designed gas chamber.The coupling efficiency of the gas chamber to methane near infrared laser reaches to 93.2%,and the high coupling efficiency and high stability of the gas chamber is verified through experiments.Finally,the measurement experiment system was built,the system calibration was carried out,the technical specifications of the system was calculated and the gas concentration was measured.The measurement results show that the sensitivity of the measurement system is 0.02 mV/ppm,the stability of the measurement system is 0.12%and the maximum measurement relative error is 0.149%,the indication value measured by the system has a good linear relationship with the theoretical value,the system possesses the merits of stable,reliable,high accuracy,strong anti-interference ability and etc.